1. Field of the Invention
The present invention relates generally to a gear shift apparatus for a manual transmission for use in a vehicle such as an automotive vehicle, and more particularly, to a gear shift apparatus for a manual transmission which comprises a mis-shift preventing mechanism for preventing a driver from erroneously operating the transmission from a forward gear stage to a reverse gear stage during forward running of the vehicle.
2. Description of the Prior Art
Conventionally, as a gear shift apparatus of the type mentioned above, one illustrated in FIGS. 1A-1D is known. This manual transmission has a shift pattern (for example, see FIG. 3) in which forward first through sixth gear stage positions are disposed at respective ends of three parallel lines, and an additional reverse gear stage position defined outside the fifth or sixth gear stage position in a select direction indicated in FIG. 3. The gear shift apparatus 80 also comprises an interlock 81 connected to a transmission lever (not shown) through a cable for pivotal movement associated with a selecting manipulation of the transmission lever in the select direction to perform a gear shift operation; and a solenoid (not shown) for restricting the pivotal movement of the interlock 81 to prevent a miss shift manipulation of the transmission lever from a forward gear stage position to the reverse gear stage position during forward running of the vehicle.
The interlock 81 is pivotable about a vertical axis to take the following four select positions associated with a selecting manipulation of the transmission lever. Specifically, the interlock 81 is pivoted to a first-second speed select position (a position indicated by solid lines in FIG. 1D) at which the first-speed or second-speed gear stage can be selected; a neutral position (a position indicated in FIG. 1A) at which the third-speed or fourth-speed gear stage can be selected; a fifth-sixth speed select position (a position indicated by solid lines in FIG. 1B) at which the fifth-speed or sixth-speed gear stage can be selected; and a reverse select position (a position indicated in FIG. 1C) at which the reverse gear stage can be selected.
The interlock 81 also comprises two cams 82, 83 which are spaced apart from each other. The cam 83 has an inclined cam face 83a which opposes the cam 82.
The solenoid is electrically connected to a controller, not shown, which turns the solenoid ON when the vehicle speed is equal to or higher than a predetermined vehicle speed and OFF when the vehicle speed is lower than the predetermined vehicle speed. A pin 84 is coupled to a leading end of a plunger of the solenoid, and is urged upward by a return spring, not shown. This causes the pin 84 to move in the vertical direction as the solenoid is turned ON/OFF (energized/deenergized), and holds the pin 84 at a lower restraint position (see FIGS. 1A, 1B) when the solenoid is ON and at an upper release position (see FIG. 1C) when the solenoid is OFF. As illustrated in FIG. 1A, the pin 84 is positioned between both cams 82, 83 when the pin 84 is held at the restraint position with the interlock 81 remaining at the neutral position.
In the gear shift apparatus 80, the interlock 81 operates associated with a selecting manipulation of the transmission lever, as described below. Specifically, when the vehicle speed is lower than the predetermined vehicle speed, the pin 84 is held at the release position, thereby permitting the interlock 81 to smoothly pivot to any of the aforementioned four select positions associated with a selecting manipulation of the transmission lever, without hitting the pin 84.
On the other hand, when the vehicle speed is equal to or higher than the predetermined vehicle speed, the pin 84 is held at the restraint position, in which case the cam 82 abuts to the pin 84 as illustrated in FIG. 1B when the interlock 81 is pivotally moved from the neutral position to the fifth-sixth speed select position, associated with a selecting manipulation of the transmission lever. As a result, the interlock 81 is blocked from pivoting to the reverse select position illustrated in FIG. 1C, thereby preventing a miss shift manipulation to the reverse gear stage position during forward running.
As the interlock 81 is pivotally moved from the neutral position to the first-second speed select position, the cam 83 abuts to the pin 84 as illustrated in FIG. 1D to forcedly push up the pin 84 through the cam face 83a. Consequently, the interlock 81 is permitted to pivotally move to the first-second speed select position, with the result that a selecting manipulation (shifting manipulation) can be made to the first-speed or second-speed gear stage by the transmission lever.
Further, when the pin 84 is erroneously held at the restraint position due to the stuck solenoid, in spite of the vehicle speed lower than the predetermined vehicle speed, the pin 84 is also pushed up forcedly by the cam face 83a by a pivotal movement of the interlock 81 from the neutral position to the first-second speed select position, associated with a selecting manipulation of the transmission lever. This can forcedly release an erroneous gear shift disabled state, in which the transmission lever cannot be shifted to the reverse gear stage position, due to a stuck electromagnetic actuator or the like, thus permitting a gear shift manipulation to the reverse gear stage position.
In the conventional gear shift apparatus 80, a horizontal force (moment) generated by a pivotal movement of the interlock 81 about the vertical axis is converted to a vertical force for pushing up the pin 84 through the inclined cam face 83a, when the pin 84 is pushed up, in order to forcedly release the gear shift preventing state. Thus, due to an extremely small vertical component force relative to the horizontal force acting on the pin 84 from the cam face 83a, a large force is required for manipulating the transmission lever for selection, when the gear shift preventing state is forcedly released, resulting in a problem that the driver has a bad manipulation feeling.
The present invention has been made to solve the foregoing problem, and it is an object of the invention to provide a gear shift apparatus for a manual transmission which utilizes an actuator to prevent a miss shift manipulation from a forward gear stage to a reverse gear stage, wherein the gear shift apparatus allows a driver to perform a selecting manipulation with a small force for forcedly releasing a miss shift preventing state and therefore have a light gear shift feeling.
To achieve the above object, the present invention provides a gear shift apparatus for a manual transmission having a shift pattern comprised of a plurality of forward select positions for selecting a plurality of forward transmission gear stages, respectively, and a reverse select position arranged outside said plurality of forward select positions for selecting a reverse transmission gear stage, for selecting one of said plurality of forward transmission gear stages and said reverse transmission gear stage through a selecting manipulation and a shifting manipulation.
The gear shift apparatus of the present invention is characterized by comprising a select cam responsive to the selecting manipulation to pivotally move to a plurality of forward positions and a reverse position corresponding to the plurality of forward select positions and the reverse select position, respectively, to permit a selection by the shift manipulation from the plurality of forward transmission gear stages and the reverse transmission gear stage; a restraint cam pivotally movable between a prohibiting position at which the restraint cam comes into engagement with the select cam to prohibit the select cam from pivotally moving to the reverse position, and a permitting position at which the restraint cam is retraced from the prohibiting position to permit the select cam to pivotally move to the reverse position; urging means for urging the restraint cam toward the permitting position; an actuator coupled to the restraint cam, the actuator having a moving element for driving the restraint cam from the permitting position to the prohibiting position; and prohibition releasing means for pressing the restraint cam into a pivotal movement from the prohibiting position to the permitting position when the select cam is pivotally moved toward a forward position in response to the selecting manipulation toward a forward select position while the select cam is prohibited from pivotally moving to the reverse position by the restraint cam remaining at the prohibiting position.
In the gear shift apparatus described above, the urging means may be a twisted coil spring, and the actuator may be a solenoid which has a plunger as the moving element.
According to this gear shift apparatus for a manual transmission, the restraint cam is held at the permitting position by an urging force of the urging means when the actuator is inoperative, permitting the select cam to pivotally move to the reverse direction, so that the transmission can be shifted to the reverse transmission gear stage. On the other hand, as the actuator is driven, the restraint cam is pressed by the moving element from the permitting position to the prohibiting position against an urging force of the urging means, thereby prohibiting the select cam from pivotally moving to the reverse position. As a result, the driver is prohibited from performing a manipulation for selecting the reverse select position, to prevent an erroneous shift to the reverse transmission gear stage.
When the driver performs a manipulation for selecting a forward select position for selecting a forward transmission gear stage in the miss shift preventing state in which the restraint cam is held at the prohibiting position, the prohibition releasing means of the select cam responsively presses the restraint cam into a pivotal movement from the prohibiting position to the permitting position. Thus, the moving element can be moved from the prohibiting position to the permitting position together with the restraint cam against a driving force of the actuator. Therefore, even if a shift to the reverse transmission gear stage is erroneously disabled due to the actuator which is stuck when the restraint cam remains at the prohibiting position, such a situation can be released by force. In this event, since two cams are used, the gear shift disabled state can be forcedly released in an efficient manner through the transmission of a torque from the pivotally moved select cam to the restraint cam, as compared with the conventional release operation which relies on the transmission of a horizontal force as a vertical force through a cam face. Consequently, the miss shift preventing state or gear shift disabled state can be released with a much lighter force than before.
Preferably, in the gear shift apparatus for a manual transmission described above, the distance between the center of pivotal movement of the restraint cam and a location of the select cam pressed to the prohibition releasing means is set to be longer than the distance between the center of pivotal movement of the restraint cam and a location of the restraint cam contacted to the moving element.
According to this preferred embodiment of the gear shift apparatus for a manual transmission, since the distance between the center of pivotal movement of the restraint cam and a location of the select cam pressed to the prohibition releasing means is set to be longer than the distance between the center of pivotal movement of the restraint cam and a location of the restraint cam contacted to the moving element, the restraint cam can be driven with a smaller torque of the select cam in accordance with the principles of lever during a selecting manipulation. As a result, the miss shift preventing state or erroneous gear shift disabled state can be released with a yet smaller force than before, permitting the driver to have a lighter gear shift feeling.